The present invention relates to an improved stator for an electromagnetic transducer.
Alternators are commonly employed as the basic source of electrical power in automotive vehicles. The alternator output is rectified, and is used to charge the vehicle battery and to operate a variety of electrical devices incorporated in the vehicle. Recent changes in standard or customarily ordered optional equipment for such vehicles, such as electrically heated rear windows, air conditioners, CB radios, etc., have imposed heavier power requirements on the vehicle alternator than heretofore. As a consequence, alternators of increased capacity are needed, requiring an increase in the size and the weight of the alternator. Unfortunately, increased size and weight is contraindicated by the limited space available within the engine compartments of late model automobiles and the need to minimize the weight thereof.
The rotary electromagnetic excitation structures of alternators include a series of alternate north and south magnetic rotor poles disposed concentrically with the stator and separated from the stator poles by a small gap. Most automotive alternators utilize a complete rotary excitation structure, including an excitation coil which rotates with the rotor, so that the exciting current for the coil must be applied through brush and slip-ring circuit connections. On the other hand, some alternators are of the so-called "brushless" construction, in which the exciting coil is stationary so that slip-rings and brushes can be eliminated. Brushless alternators afford substantial advantages with respect to elimination of the wear and maintenance problems associated with slip-rings and brushes. An excellent example of a brushless alternator construction is set forth in Barret U.S. Pat. No. 3,953,753, issued Apr. 27, 1976.
The alternators employed in vehicles are usually three-phase machines, and have stator windings which ordinarily comprise three multi-coil winding sections with the coils of each section connected in series. Conventionally, each coil in each section encircles three stator poles, and the coils of each section may be separated from each other by one to three stator poles that are not encircled by any coil of that section. In the aforementioned Barrett patent, an improved stator winding is provided wherein each coil in each winding section encompasses two stator poles, and is separated from the next adjacent coil in the same section by at least one pole not encompassed by a coil of that section, and wherein each winding section is angularly displaced around the stator relative to each of the other two sections.
To increase the power output from such alternators generally requires an increase in the number of turns in the coils of the winding sections which, with conventional stators, requires an increase in the size of the stator to accommodate the additional turns, and therefore an increase in the size of the alternator. For certain applications this may not be practical or desirable.